This disclosure relates to lighting fixtures, and more particularly to lighting fixtures that employ a light source which includes distinct, multiple light sources that collectively provide a desired, adequate lumen output in a desired photometric pattern.
Light fixtures have been employed to provide illumination for a wide variety of applications including, for example, parking garages to increase safety. Recently, light emitting diode (LED) technology has sufficiently advanced that LEDs may be used as the light source for these types of light fixtures. One challenge created by LED's is the dissipation of heat from the LED's. Heat has at least two detrimental effects on an LED. First, light output is inversely proportional to the junction temperature of an LED, thus the higher the temperature, the less light emitted by the LED. Second, the life span of the LED is also inversely proportional to the junction temperature of an LED, so the higher the temperature, the quicker the LED degrades over time. Therefore, the heat created when the LED produces light must be dissipated to improve the light output and life span of the LED. Conventional LED light fixtures often include heat sinks with fins which are grouped together and protrude vertically from a top of the fixture. However, this method and arrangement may stifle airflow, which is an important factor in dissipating heat. This is especially true when mounting the fixture close to or against the ceiling. Also, physical obstructions, e.g., a bird nest, may be situated on a top surface created by the fins, and the nest insulates the fins which reduces the ability to dissipate the heat generated by the LEDs and drivers.
Further, a uniform illumination is desired in lighting applications to reduce shadows and glare. Some conventional light fixtures for parking garages create bright portions (usually close to the center of the associated area or nadir), and dim portions (usually near the periphery of the associated area). Conventional light fixtures also may adversely impact vision by producing glare. Thus there is a continuing need for an LED light fixture which reduces glare, uniformly lights an associated area, and effectively dissipates the heat generated by the LED light source.